Expression of glutamine-synthetase genes in cotyledons of germinating Phaseolus vulgaris L.

Swarup, Ranjan; Bennett, Malcolm J.; Cullimore, Julie V.

doi:10.1007/bf00197566

Cited by 14 publications

(9 citation statements)

References 31 publications

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“…The gln-~ gene is the predominantly expressed GS gene both in plumules at this early stage (Figs. 2 and 3) and, interestingly, also in radicles [31 ] and cotyledons [ 34 ]. Following initiation of imbibition there is an exponential increase in leaf fresh weight, dry weight and blade area up to day 8 [15].…”

Section: Differential Expression Of the Gs Gene Family In Developing mentioning

confidence: 94%

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Regulation of glutamine synthetase genes in leaves of Phaseolus vulgaris

Cock

Watson

et al. 1991

Plant Mol Biol

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Glutamine synthetase (GS) activity increased over three-fold in developing primary leaves of Phaseolus vulgaris L. This increase was shown to be the result of differential expression of three members of the GS gene family: gln-alpha and gln-beta, which encode cytosolic GS polypeptides, and gln-delta, which encodes the chloroplast-located GS. The gln-delta gene was the most highly expressed GS gene and was regulated in a complex manner with two different transcripts accumulating differentially during leaf development. This gene was expressed weakly in the dark and was induced strongly by light; this induction was shown not to be an indirect effect of photorespiration. In the long term, gln-delta showed increased expression in photorespiring compared with non-photorespiring leaves. However, in the short term, there was no induction of gln-delta following transfer of plants to photorespiratory conditions. These results suggest that regulation of gln-delta by photorespiration was the result of indirect, long-term effects on cellular metabolism. In general, in all these experiments, analysis of cytosolic versus chloroplastic GS polypeptides and of the GS isoenzyme profiles showed the same pattern of changes in abundance as that observed for the mRNAs suggesting that regulation of GS gene expression occurred primarily at the mRNA level. However, it was noteworthy that the delta isoenzyme remained at a high abundance in older leaves, grown in both light and dark, despite a decrease in abundance of gln-delta mRNA.

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Section: Differential Expression Of the Gs Gene Family In Developing mentioning

confidence: 94%

“…vulgaris in a number of organs including nodules, roots and cotyledons [3,4,11,13,20,22,31,32,34]. The work presented here wes designed to examine how this small gene family is regulated in developing leaves and to examine the effects of light and photorespiration on GS gene expression in this organ.…”

Section: Introductionmentioning

confidence: 99%

Regulation of glutamine synthetase genes in leaves of Phaseolus vulgaris

Cock

Watson

et al. 1991

Plant Mol Biol

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“…Total RNA was isolated from roots, leaves, stems, petioles, flowers, and dry seeds, as well as from mature nodules (28 d postinoculation) and germinating seeds. In the latter two situations, large amounts of Gin are synthesized, and GS activity has been shown to increase (Walker and Coruzzi, 1989;Swarup et al, 1990;McGrath and Coruzzi, 1991). Gene-specific probes were prepared from DNA fragments encompassing the divergent 3' noncoding sequences of the three genes ( Fig.…”

Section: Family In M Truncatulamentioning

confidence: 99%

Differential Expression within the Glutamine Synthetase Gene Family of the Model Legume Medicago truncatula

et al. 1993

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The glutamine synthetase (CS) gene family of Medicago truncatula Caertn. contains three genes related to cytosolic GS (MtCSa, MtCSb, and MtCSc), although one of these (MtGSc) appears not to be expressed. Sequence analysis suggests that the genes are more highly conserved interspecifically rather than intraspecifically: MtCSa and MtCSb are more similar to their homologs in Medicago sativa and Pisum sativum than to each other. Studies in which gene-specific probes are used show that both MtCSa and MtCSb are induced during symbiotic root nodule development, although not coordinately. MtCSa is the most highly expressed CS gene in nodules but is also expressed to lower extents in a variety of other organs. MtCSb shows higher levels of expression in roots and the photosynthetic cotyledons of seedlings than in nodules or other organs. In roots, both genes are expressed in the absence of an exogenous nitrogen source. However the addition of nitrate leads to a short-term, 2-to 3-fold increase in the abundance of both mRNAs, and the addition of ammonium leads to a 2-fold increase in MtCSb mRNA. The nitrogen supply, therefore, influentes the expression of the two genes in roots, but it is clearly not the major effector of their expression. In the discussion section, the expression of the CS gene family of the model legume M. truncatula is compared to those of other leguminous plants.GS (EC 6.3.1.2) is a key enzyme in the nitrogen metabolism of higher plants, catalyzing the assimilation of ammonium to form Gln. This ammonium is derived from the primary nitrogen sources of the plant (through the reduction of soil nitrate and, in the case of legumes, by the symbiotic fixation of atmospheric nitrogen), as well as from other metabolic pathways such as photorespiration, phenylpropanoid metabolism, and the catabolism of amino acids (Lea et al., 1990). These pathways occur to varying extents in different tissues and subcellular locations, which is reflected by the fact that in higher plants GS exists as a number of distinct isoenzymes located in both the cytosol and the chloroplast, which have different activities in different organs (McNally and Hirel, 1983). These multiple isoenzymes are encoded by a small family of genes that, in tum, have been shown to be differentially expressed in both a developmental-and organ-'This work was supported by a fellowship to A.C.S. from the

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“…In gramnegative bacteria, GS has been shown to be regulated by cumulative feedback inhibition, covalent modification, and repressionl derepression (Shapiro and Stadtman, 1970;Stadtman, 1990). There are, however, few reports concerning the posttranslational regulation of GS in plant systems (Hemon et al, 1990;Swarup et al, 1990;Hoelzle et al, 1992;Temple et al, 1993). Root GS activity in French bean, pea, and soybean was found to be stimulated significantly following treatment with NH, and nitrate, even though equal numbers of GS subunits were present in both nitrogentreated and untreated roots (Hoelzle et al, 1992).…”

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“…Similar observations have been made in Lemna minor, and the authors (Rhodes et al, 1978) suggested that GS protein is maintained in an inactive form unless sufficient nitrogen and carbon skeletons are available for Gln synthesis. Some recent papers have reported instances in which a specific GS, transcript level was found to significantly exceed the corresponding protein level, suggesting regulation at a level downstream of transcription (Hemon et al, 1990;Swarup et al, 1990;Temple et al, 1993). Chaperones related to chaperonin-60 have also been implicated in the assembly/folding of GS, in the leaves of some plants (Lubben et al, 1989;Tsuprun et al, 1992).…”

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Total Glutamine Synthetase Activity during Soybean Nodule Development Is Controlled at the Level of Transcription and Holoprotein Turnover

et al. 1996

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Cln synthetase (CS) catalyzes the ATP-dependent condensation of ammonia with glutamate to yield Cln. I n higher plants CS is an octameric enzyme and the subunits are encoded by members of a small multigene family. I n soybeans (Glycine max), following the onset of N, fixation there is a dramatic increase in CS activity in the root nodules. CS activity staining of native polyacrylamide gels containíng nodule and root extracts showed a common band of activity (CSrs). The nodules also contained a slower-migrating, broad band of enzyme activity (CSns). The GSns activity band i s a complex of many isozymes made up of different proportions of two kinds of CS subunits: GSr and CSn. Root nodules formed following inoculation with an Nif-strain of Bradyrhizobium japonicum showed the presence of CS isoenzymes (CSnsl) with low enzyme activity, which migrated more slowly than CSns. Csnsl is most likely made up predominantly of CSn subunits. Our data suggest that, whereas the class I GS genes encoding the CSr subunits are regulated by the availability of NH3, the class II GS genes coding for the CSn subunits are developmentally regulated. Furthermore, we have demonstrated that the CSnsl isozymes in the Nif-nodules are relatively more labile. Our overall conclusion is that CSns activity in soybean nodules is regulated by N, fixation both at the level of transcription and at the level of holoprotein stability.GS (EC 6.3.1.2) is a key enzyme in the assimilation of NH,, catalyzing the ATP-dependent condensation of NH, with glutamate to yield Gln (Lea et al., 1990). The NH, is derived from symbiotic N, fixation, the reduction of NO,-or NO,-, photorespiration, or amino acid catabolism (Hirel et al., 1993). The reaction is believed to proceed via a two-step process, the first involving the formation of GSbound glutamyl phosphate from ATP and glutamate, followed by the addition of NH, to form a tetrahedral adduct with the subsequent liberation of Gln, ADP, and Pi (Lea and Ridley, 1989).

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Expression of glutamine-synthetase genes in cotyledons of germinating Phaseolus vulgaris L.

Cited by 14 publications

References 31 publications

Regulation of glutamine synthetase genes in leaves of Phaseolus vulgaris

Regulation of glutamine synthetase genes in leaves of Phaseolus vulgaris

Differential Expression within the Glutamine Synthetase Gene Family of the Model Legume Medicago truncatula

Total Glutamine Synthetase Activity during Soybean Nodule Development Is Controlled at the Level of Transcription and Holoprotein Turnover

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